This invention relates to a process for the purification of water by distillation using directly solar energy.
The desalination of sea water by means of apparatus using solar energy has been practiced for a long time. Nevertheless the importance of the capital investment and of the relative cost of treatment with various known distillation apparatuses which use solar energy renders prohibitive the manufacturing cost of the water by means of these forms of apparatus and prohibits the general employment thereof.
All the apparatuses hitherto used include the application of the physical phenomenon known under the name of "conservatory effect", this phenomenon, when it occurs, is profitably utilised to warm the water and cause its evaporation under the action of solar radiation passing through a transparent cover made of plastic material or of glass. Because of the existence of a temperature difference between the interior and the exterior of the conservatory, some of the water vapour condenses on the cover and it remains to capture further desalinated water thus formed.
Experience has shown that the apparatuses of the type which have just been mentioned are inherently expensive and, moreover, that their constructional cost is directly proportional to the surface area provided and consequently to the quantity of the water to be obtained. Some apparatuses incorporate the construction of a pan entirely covered by a transparent roof which plays the part of a condensation unit, a sealing unit for the pan and a reservoir for appropriate removal. The construction of the transparent roof and the obtaining of the sealing of the fixing of the roof on the pan constitute two expensive features of the arrangement for which it is necessary to adapt the measures to be taken to cater satisfactorily for the requirements of the resistance to corrosion and the chemical inertness to solar radiation of the constituent parts of these apparatuses in order to ensure a mechanical stability enabling them to withstand strong winds.